Target image rendering with color transparencies

Abstract

An image generation system (50) for generating three independent monochromatic images, using three monochromatic CRT projectors (56, 58, 60). An image generator (52) produces synchronized video signals representing the images, which drive the projectors. The image generator (52) is similar to a conventional image generator for a full color, single channel system, except that the red, green and blue color components are used to define separate monochromatic images which can overlap and still be fully rendered.

What is claimed is: 
     
       1. An image projecting system for projecting three independent monochromatic images using a single color image generation channel, comprising: a single full color image generation channel comprising a color image generator for generating red, green and blue video signals nominally representing the color components of a single full color image, and a synchronization signal;   first, second and third monochrome image projection means each responsive to a given one of said red, green or blue video signals and to said synchronization signal for projecting first, second and third independent monochrome foreground images corresponding to said respective red, green and blue video signals;   wherein said color image generator further comprises image transparency generation means for rendering transparent, only with respect to operations of said image generator, each image component represented by said red, green, and blue video signals so that each image component may be seen through the others, and wherein color other than that of the foreground image component is made to mix in an additive sense so that superimposed monochromatic images yield composite colors over the overlapped portions of the foreground image component.   
     
     
       2. The system of claim 1 wherein each of said first, second and third monochrome image projection means comprises a monochrome projection cathode ray tube (CRT) controlled by said respective red, green or blue video signal and said synchronization signal. 
     
     
       3. The system of claim 1 wherein said first, second and third image projection means further comprises first, second and third pointing apparatus to independently point said respective image projection means in independently determined directions. 
     
     
       4. The system of claim 1 wherein said image transparency generation means comprises means for passing through without change all background colors which are not overlapped by other images. 
     
     
       5. The system of claim 4 wherein each color component within said image generator comprises a target image, and said image transparency means comprises means for implementing the following transparency algorithm: for a red video signal representing a foreground target image:   B.sub.f =G.sub.f =0 for all components;                    (4)       T.sub.b =T.sub.g =1 for all components;                    (5)       B.sub.b =B.sub.v ; G.sub.b =g.sub.v ; (R.sub.b -R.sub.f)*T.sub.r +R.sub.f =R.sub.v ;                                                (6)       for a green video signal representing a foreground target image:   R.sub.f =B.sub.f =0 for all components;                    (7)       T.sub.r =T.sub.b =1 for all components;                    (8)       R.sub.b =R.sub.v ; B.sub.b =B.sub.v ; (G.sub.b -G.sub.f)*T.sub.g +G.sub.f =G.sub.v ;                                                (9)       for a blue video signal representing a foreground target image:   R.sub.f =G.sub.f =0 for all components;                    (10)       T.sub.r =T.sub.g =1 for all components; and                (11)       R.sub.b =R.sub.v ; G.sub.b =Gv; (B.sub.b -B.sub.f)*T.sub.b +B.sub.f =B.sub.v ;                                                (12)        where T r , T g , T b  designate red, green and blue transparency with 1=transparent and 0=opaque; R b , R f , R v  designate background, foreground and viewed red components respectively; G b , G f , G v  designate background, foreground and viewed green components, respectively; and B b , B f , B v  designate background, foreground and viewed blue components, respectively.   
     
     
       6. A method for projecting three independent monochromatic target images using a single color image generation channel comprising a color image generator for generating first, second and third video signals nominally representing the respective red, green and blue components of a single full color target image, and a synchronization signal, comprising a sequence of the following steps: providing first, second and third monochrome image projection means for projecting first, second and third monochrome target images;   generating said first, second and third video signals to represent independent first, second and third independent target images;   driving said first, second and third monochrome image projection means with said respective firsts, second and third video signals and said synchronization signals to project said first, second and third monochrome target images corresponding to said respective first, second and third video signals; and   independently controlling the pointing of said first, second and third image projection means so that the respective projected positions of said respective target images are independent of the positions of the other of said projected target images.   
     
     
       7. The method of claim 6 wherein said step of generating said first, second and third video signals comprises the step of passing through without change all background image colors which are not overlapped by other images. 
     
     
       8. The method of claim 7 wherein each color component representation within said image generator comprises a target image, and said step of generating said first, second and third video signals comprises implementing the following transparency algorithm: for a red video signal representing a foreground target image:   B.sub.f =G.sub.f =0  for all components;                   (4)       T.sub.b =T.sub.g =1 for all components;                    (5)       B.sub.b =B.sub.v ; G.sub.b =G.sub.v; (R.sub.b -R.sub.f)*T.sub.r +R.sub.f =R.sub.v ;                                                (6)       for a green video signal representing a foreground target image:   R.sub.f =B.sub.f =0 for all components;                    (7)       T.sub.r =T.sub.b =1 for all components;                    (8)       R.sub.b =R.sub.v ; B.sub.b =B.sub.v ; (G.sub.b -G.sub.f)*T.sub.g +G.sub.f =G.sub.v ;                                                (9)       for a blue video signal representing a foreground target image:   R.sub.f =G.sub.f =0 for all components;                    (10)       T.sub.r =T.sub.g =1 for all components; and                (11)       R.sub.b =R.sub.v ; G.sub.b =Gv; (B.sub.b -B.sub.f)*T.sub.b +B.sub.f =B.sub.v ;                                                (12)        where T r , T g , T b  designate red, green and blue transparency with 1=transparent and 0=opaque; R b , R f , R v  designate background, foreground and viewed red components respectively; G b , G f , G v  designate background, foreground and viewed green components, respectively; and B b , B f , B v  designate background, foreground and viewed blue components, respectively.